1. Field of the Invention
The present invention relates to electroplating racks and more particularly to a novel and improved rack for supporting a plurality of relatively thin elongated articles in spaced relationship for electroplating.
2. Prior Art
In modern automatic plating systems, a plurality of rack assemblies are used to support articles to be plated. The racks are hung on a bus bar positioned above tanks containing cleaning, plating and washing solutions. A programmed drive system sequentially moves the racks along the bus bar to prescribed stations over the tanks, lowers the bus bar to submerge the articles in the tank-carried solutions, and raises the bus bar to drain the solutions from the articles and racks before the racks are advanced to the next station.
The articles to be plated are used as cathodes of an electrolytic cell. The anode is formed from the metal to be plated. The electrolyte is a metal salt solution which presents ions of the plating metal to the cathode for deposition. As metal ions are depleted from the electrolyte, they are replenished by the anode.
The racks must be capable not only of securely holding a plurality of articles in properly spaced relationship, but must also provide a low impedence current path and make good electrical contact with the supported articles. Only a minimum surface area of the articles can be shielded from the electrolyte. The racks must be capable of holding a maximum number of articles to accommodate high production volumes, and yet must be of sufficiently simple construction so that circulation of the electrolyte is not inhibited.
Ideally the racks incorporate a minimum number of parts so they can be economically manufactured. The racks should occupy a minimum of storage space. The racks should be capable of accommodating different sizes of articles in an efficiently spaced arrangement.
Still another consideration of the design of electroplating racks is they must permit the expedient racking and unracking of articles.
A number of proposals have been made in the prior art to provide electroplating racks designed to accommodate long, thin articles. Many of these proposals are designed to suspend the long articles horizontally. Horizontal suspension is undesirable for a number of reasons, including the fact that it necessitates the use of long tanks to hold the cleaning, plating and washing solutions. When these long tanks are placed side-by-side in an automated production system, the system occupies an unacceptably large amount of floor space.
Most known racks which support long articles vertically are not well adapted to accommodate articles of a wide variety of sizes. Typically the racks are designed to accommodate a prescribed number of long articles regardless of their size. While such racks may efficiently hold two dozen articles having a relatively large cross-section in closely spaced relationship, two dozen smaller cross-section articles supported at the same on-center spacing is a highly inefficient arrangement.
A number of prior plating racks which are arranged to vertically support long articles use hooks which engage the upper end regions of the articles. Hook-support systems leave lower portions of the long articles free to dangle and to move relative to their supporting rack. If such relative movement occurs when a rack full of articles is being lowered into a plating tank, some of the articles may not enter the tank and may jam the operation of the automated system which positions the racks. If such relative movement occurs while the articles are being moved while suspended in a plating tank, the articles can tangle with an adjacent rack and cause the automated system to jam.